A prosthetic device, or prosthesis, is an artificial substitute for a part of the body such as a limb. Numerous prostheses have been developed to serve this purpose, each trying to replicate the function and appearance of the missing body part. Limb prostheses have been previously described in U.S. Pat. No. 5,545,234 to Collier Jr. and U.S. Pat. No. 5,800,570 to Collier, which are hereby incorporated by reference.
Most prosthetic devices have sockets that receive an amputee's residual limb. There are generally two categories of sockets: hard socket systems wherein the residual limb fits directly into the socket without any type of liner or sock, and soft socket systems which utilize a liner or insert. With either category of socket, the challenge is to keep the residual limb tightly confined within the socket so as to maintain the prosthetic device on the residual limb. The more active a prosthetic device user is, the more important it is to have the prosthetic device maintained in a tight association with the residual limb. Loss of a prosthetic device can cause a user to fall and suffer serious injury.
There are various methods of maintaining prosthetic devices on the residual limbs of users. Prosthetic devices may, for example, be suspended from a user's body by some form of pulley, belt or strap suspension. Such prosthetic devices may employ various harnesses and/or lacings. Sleeve suspensions also may be used. Such prosthetic devices may employ a constrictive rubber sleeve tube rolled over the top of their prosthetic device and onto the upper aspect of their residual limb. Such a sleeve suspension may be used in combination with other forms of suspension.
Other systems may employ electric or mechanical pumps that establish positive or negative pressure to maintain prosthetic devices on the residual limb of users. However, these systems typically look unnatural, are heavy, and are often difficult to use. Further, these systems may require pressures that are so forceful that there is a risk of damage to residual limb tissue, such as generalized trauma, vascular disruption, tissue atrophy, and sequential loss of tissue. For example, some systems utilize mechanical hand pumps to draw negative pressure from within the prosthetic device. These pumps typically are difficult to use, and require frequent pumping to counteract leakage of air into the prosthetic device. Other systems utilize an electrical motor-driven pumps to establish negative or positive pressure within the prosthetic device. These pumps typically are heavy, and require relatively high pressure to maintain the prosthetic device on the residual limb. Yet another system uses a weight-actuated mechanical pump to draw negative pressure within a lower limb prosthetic device. Such pump typically is attached to the prosthetic foot, and acts like a shock absorber. The pump is bulky, heavy and unnatural looking, and requires the user to apply downward pressure to actuate the pump.
There is a need to provide a lightweight prosthetic device that employs a mechanical pump to establish a negative pressure within the device for attachment to the residual limb of a user. Such a lightweight device would allow a user to attach the prosthetic device to the residual limb with lower negative pressures. There is also a need to provide a natural looking device that creates or maintains negative pressure during normal ambulatory motion by a user. Finally, there is a need to provide a device with a pump that may be adjusted to provide more or less draw based on the physical characteristics and activity level of the user.